Translations:Introduction - Chapter 15/9/en

Man-made systems and short-run natural systems can be unstable, and finding ways to stabilize them represents an important aspect of systems analysis. If all the zeros as well as the poles lie outside the unit circle (in the digital case) or within the left half-plane (in the analog case), the transfer function represents a special kind of stable causal system called a minimum-delay (or minimum-phase) system. In a nutshell, a minimum-delay system is one that is invertible in real time, and that is a major reason why such systems are important.